The invention relates to a device for actuating grippers in a machine for processing sheetlike material, such as a sheet-processing rotary printing machine, wherein sheets are transported by grippers.
The published German Patent Document DE 42 00 406 A1 is concerned with a gripping device in sheet-processing machines. The grippers for a sheet-like material are fastened on a gripper operating shaft. The grippers are opened and closed simultaneously via a cam control device. By employing the teachings provided in this published German patent document, individual grippers or groups of grippers on the circumference of a sheet-guiding cylinder are activated independently of one another. A control device which activates the grippers is provided for this purpose, the control device including at least one sensor, an opening and/or closing mechanism for the grippers and a computer. The control device actuates the opening and/or closing mechanisms at a prescribed machine position or setting. The sensors used in this heretofore known construction are angle-of-rotation sensors or paper-position sensors, in order to detect either the position of the cylinder or the position of the sheet-like material, and then to actuate the opening and closing mechanism.
The published European Patent Document EP 0 775 576 B1 is concerned with a gripper control device for a cyclically oscillatingly driven pre-gripper for transporting individual sheets in a sheet-fed printing machine. This published document discloses a gripper control device for a cyclically oscillatingly driven pre-gripper accommodated at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the pre-gripper having at least one sheet gripper. The sheet gripper is forcibly movable about a joint pin aligned parallel to the pivot pin, by cams for closing and opening purposes, as the sheets are received and transferred. One of the cams revolves with a single revolution and, in the course thereof, pivots the other cam, which is pivotably mounted on a stationary roller lever. The position of the cams determines the points in time at which the gripper closes and opens.
A switching mechanism is provided in order to fix the pivotable cam, this cam having a gripper-closing region and a gripper-opening region. The gripper-closing region is additionally provided with a gripper-opening region, the additionally arranged gripper-opening region having assigned thereto, for compensation purposes, an additional gripper-closing region on the single-revolution cam.
In order to produce closing or opening movements of sheet-gripping grippers, use has been made heretofore, in particular, of mechanical cam mechanisms, and occasionally also coupler mechanisms. These drives have the disadvantage that usually a fixed mechanical coupling is provided for the main machine drive, and that it is not possible to change the movement due to the kinematic dimensioning. This means that the movement cannot readily be adapted during operation to changed boundary conditions, e.g., a different printing-material thickness. In the case of double-sheet detection, mechanical barriers prevent the grippers from closing, so that the double-sheet formation cannot be gripped and conveyed into the machine. This improvement or solution, however, involves great mechanical outlay in order to realize the basic functions such as gripper control, paper-thickness adaptation and defective-sheet detection. The entire xe2x80x9cpre-gripperxe2x80x9d system is subjected to disruptive force action during the gripper actuation, and this solution also causes the machine to be subjected to a retroactive torque effect. The system used for closing the grippers during double-sheet detection requires long reaction times and takes up installation space in printing units. Furthermore, using the aforementioned improvements or solutions for producing the closing and opening movements of sheet-gripping grippers, movement can only be introduced at the ends of the gripper shaft.
In view of improvements or solutions heretofore known from the prior art, and of the technical problems which are presented, it is an object of the invention to provide a gripper control which requires only low mechanical outlay, performs the functions required of the gripper control and has as little effect as possible on the movement of a pre-gripper.
With the foregoing and other objects in view, there is provided, in accordance with a first aspect of the invention, a pre-gripper driving device for a pre-gripper cyclically driven oscillatingly and serving for transporting individual sheets in a sheet-processing machine, comprising sheet grippers disposed at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the sheet grippers being movable relative to a gripper support about a gripper shaft aligned parallel to the pivot pin, for closing and opening the sheet grippers, and an activatable and regulatable drive for producing the movement of the grippers, the drive, on one hand, being connected to the sheet grippers and, on the other hand, being supported on one of the rocking lever and the frame.
In accordance with another feature of the invention, the drive is actable centrally on the gripper shaft which serves for pivotably accommodating the sheet grippers.
In accordance with a further feature of the invention, the drive is introducible into both ends of the gripper shaft simultaneously.
In accordance with an added feature of the invention, the drive is realized as a linear drive with an extensible actuating element accommodated on the sheet grippers, respectively, at an articulation point thereon.
In accordance with an additional feature of the invention, the drive is realized as a rotary drive, serving for acting at least indirectly on the gripper shaft.
In accordance with yet another feature of the invention, the drive is realized as an actuating motor.
In accordance with yet a further feature of the invention, the actuating motor is operatively engageable with the gripper shaft via a rack and pinion.
In accordance with yet an added feature of the invention, the drive is constructed as a piezoelectric actuator.
In accordance with yet an additional feature of the invention, the drive is constructed as a piston/cylinder unit subjectible to a pressure medium.
In accordance with still another feature of the invention, the drive is a linear drive having a line of action running parallel to a direction of movement of a coupling link-mounted point of articulation of the linear drive on the pre-gripper lever.
In accordance with still a further feature of the invention, in closed condition of the sheet gripper, the point of articulation is located at least approximately on a connecting line between the gripper shaft and a point of rotation of the pre-gripper lever.
In accordance with still a further feature of the invention, in closed condition of the sheet gripper, the point of articulation is located between the gripper shaft and the pivot pin of the pre-gripper lever.
In accordance with still an added feature of the invention, a point of articulation of the drive coincides, on the frame, with the pivot point of the pre-gripper lever.
In accordance with still an additional feature of the invention, a point of articulation of the drive is disposed on the frame, and an actuating lever of the drive has a joint.
In accordance with a second aspect of the invention, there is provided a printing unit having a pre-gripper driving device for a pre-gripper cyclically driven oscillatingly and serving for transporting individual sheets in a sheet-processing machine, comprising sheet grippers disposed at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the sheet grippers being movable relative to a gripper support about a gripper shaft aligned parallel to the pivot pin, for closing and opening the sheet grippers, and an activatable and regulatable drive for producing the movement of the grippers, the drive, on one hand, being connected to the sheet grippers and, on the other hand, being supported on one of the rocking lever and the frame.
In accordance with a third aspect of the invention, there is provided a digital printing unit having a pre-gripper driving device for a pre-gripper cyclically driven oscillatingly and serving for transporting individual sheets in a sheet-processing machine, comprising sheet grippers disposed at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the sheet grippers being movable relative to a gripper support about a gripper shaft aligned parallel to the pivot pin, for closing and opening the sheet grippers, and an activatable and regulatable drive for producing the movement of the grippers, the drive, on one hand, being connected to the sheet grippers and, on the other hand, being supported on one of the rocking lever and the frame.
In accordance with a fourth aspect of the invention, there is provided a rotary printing machine having a pre-gripper driving device for a pre-gripper cyclically driven oscillatingly and serving for transporting individual sheets in a sheet-processing machine, comprising sheet grippers disposed at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the sheet grippers being movable relative to a gripper support about a gripper shaft aligned parallel to the pivot pin, for closing and opening the sheet grippers, and an activatable and regulatable drive for producing the movement of the grippers, the drive, on one hand, being connected to the sheet grippers and, on the other hand, being supported on one of the rocking lever and the frame.
In accordance with a concomitant aspect of the invention, there is provided a multicolor rotary printing machine having a pre-gripper driving device for a pre-gripper cyclically driven oscillatingly and serving for transporting individual sheets in a sheet-processing machine, comprising sheet grippers disposed at a free end of a rocking lever pivotable about a pivot pin fixed to a frame, the sheet grippers being movable relative to a gripper support about a gripper shaft aligned parallel to the pivot pin, for closing and opening the sheet grippers, and an activatable and regulatable drive for producing the movement of the grippers, the drive, on one hand, being connected to the sheet grippers and, on the other hand, being supported on one of the rocking lever and the frame.
An advantages which can be achieved by the construction proposed in accordance with the invention is, in particular, that the pre-gripper gripper control is now isolated mechanically from the main drive. In combination with a freely programmable control, which is thus independent of the main drive, flexible movement control of the grippers or gripper bars is possible by a dedicated regulatable drive, the movement control allowing, in a relatively straightforward manner, adaptation of the gripper movement to different types of operation, printing-material properties such as, for example, the printing-material thickness, and to different printing speeds. It is possible to dispense with additional, high-outlay adjustment devices and accessories.
In an advantageous possible realization of the concept upon which the invention is based, it is possible to use jointly or separately acting regulatable drives, whether they are linear drives or rotary drives, in any desired number or arrangement. It is thus possible, for example, for the drives for the sheet grippers, which are mounted on the gripper shaft, to be provided centrally on the gripper shaft or at the two ends thereof, with the result that alternatives are possible for effecting torque introduction into the gripper shaft. Depending upon the admissible torsional moment, it is also possible for the drive for actuating the gripper shaft to be introduced into both ends of the gripper shaft simultaneously.
It is possible for the drives to be constructed either as linear drives with an extensible actuating element which is accommodated on the sheet gripper directly at a point of articulation, or as a rotary drive acting directly or indirectly on the gripper shaft which accommodates the sheet grippers.
The rotary drives are configurable, for example, as actuating motors, whether they are electric motors or other drives which produce a rotary movement, while the linear drives are configurable, for example, as actuating cylinders, whether they are activated pneumatically, hydraulically or electromechanically. The movement of the drive may be transmitted indirectly by racks and pinions. It is also possible to provide piezoelectric actuators, which have a particularly quick response behavior and can convert extremely small actuating movements within extremely short periods of time. In order to improve the response behavior or to realize different actuating distances, it is possible for intermediate gear mechanisms to be accommodated between the individual enumerated drives which are possible. It is possible for the intermediate gear mechanisms, on the one hand, to be provided for adaptation to the given installation space, and they can be used for power-boosting purposes and for reducing the forces of inertia; on the other hand, self-locking may be produced by providing an intermediate gear mechanism.
The actuators for the gripper shaft, which serve as linear drives or rotary drives, may be supported either on a movable component or on a component which is fixed in relation to the machine frame. Instead of piezoelectric actuators, it is also possible to use magnetostrictive actuators in order to effect the gripper-opening and/or gripper-closing movement once the leading edge of the printing material has been gripped.
According to an advantageous different embodiment of the pre-gripper gripper drive proposed according to the invention, it is possible, using a linear drive for gripper control, for the line of action of the linear drive to run parallel to the movement direction of the coupling-like mounted point of articulation of the linear drive on the pre-gripper. In the closed state of the gripper, the point of articulation is located at least approximately on a connecting line between the gripper shaft and a point of rotation of the pre-gripper lever; furthermore, it is also possible, in the closed state of the gripper, for the point of articulation to be arranged between the gripper shaft and the pivot point of the pre-gripper lever.
With such an arrangement of the points of articulation, the linear drive, during the closing movement of the sheet grippers, assists the immediately following pivoting movement of the pre-gripper for accelerating the sheet to printing speed. As the sheet grippers are opened, the movement of the pre-gripper gripper lever can be utilized in order to accelerate the opening operation of the sheet gripper to a great extent because the movements of the linear drive and the pre-gripper lever are advantageously superposed, i.e., it is possible to utilize the advantageous relative movements for opening the sheet gripper quickly. By this arrangement, the masses which are to be moved on the pre-gripper are relatively small because it is virtually only the push rod of the linear drive, for example, formed as a piston rod, in the case of pneumatically activatable actuators, which moves along with the movement of the pre-gripper gripper lever about the pivot pin thereof. A further advantage which can be achieved by this configuration is that the linear drive is subjected only to low forces of inertia because only a relatively small, and thus slow, pivoting movement is executed. In addition, it is possible for an actuator subassembly to be accommodated in the stationary framework, which is mounted, however, for rotation. The transverse accelerations which are established are thus low, which additionally has a positive effect upon the service life of the sliding joints which are used.
The improvement proposed according to the invention for driving individual grippers or groups of grippers in the region of the pre-gripper can be used on sheet-processing machines, whether they are multicolor rotary printing machines for offset printing or digitally operating sheet-printing machines, wherein the stationary printing material is accelerated to the machine speed.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an actuator-gripper control, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: